A lot of offices use paper cups. Lots of paper cups. For water, tea, etc. Sometimes even plastic ones. A discussion on one of the yahoo groups I'm a part of brought out this. Apparently, one floor uses 4000+ paper cups in month!

A simple and effective way out - gift each employee a basic ceramic mug or even a pseud looking stell one when they join - and a hip looking bottle they can refill for water. Saves infinite plastic/paper. [Increases the amount of water a person drinks too and thats usually healthy.]

Styrofoam is even worse - its got similar problems as plastics, and more so from a health pov.

Finally, nothing quite beats "wash and reuse". Especially so for personal mugs/cups which don't really need as much water or detergent as shared ones, especially for mere swigs of water.